Experiment Questions

Photosynthesis

Photosynthesis

Name the plant that you used.

Elodea or other correctly named aquatic plant

Photosynthesis

How did you vary light intensity OR carbon dioxide concentration?

Lamp distance or wattage or quantity of NaHCO3

Photosynthesis

(i) State a factor that you kept constant during the investigation.

(ii) How did you ensure that this factor remained constant?

(i) carbon dioxide or light or temperature (ii) NaHCO3 or lamp distance or wattage or

water bath or described

Photosynthesis

How did you measure the rate of photosynthesis?

bubbles or volume / time OR data logger / sensor named

Photosynthesis

For which purpose did you use an aquatic plant such as pondweed rather than a terrestrial

plant when investigating the rate of photosynthesis.

To see (or measure ) gas (or bubbles)

Photosynthesis

An aquatic plant, such as the pond weed Elodea, is usually used for such an experiment. Explain why an aquatic plant is used in preference to a

land plant such as a geranium.

It is easier to see the production of oxygen in an aquatic plant

Photosynthesis

• Explain how you varied the environmental factor that you were investigating in the course of your practical work.

•

• Light intensity: bring lamp of fixed wattage stepwise nearer to the pondweed OR

• Carbon dioxide: use different concentrations of carbon dioxide in the water

Photosynthesis

In what units did you express the rate of photosynthesis?

Bubbles of oxygen /per minute

Photosynthesis

Why is a water plant rather than a land plant used in this experiment?

Ease of measurement of rate or explained

Photosynthesis

How is the temperature kept constant in this experiment?

Water bath or described

Photosynthesis

If pond water is used in the experiment, it is likely to contain dissolved carbon dioxide.

Suggest two possible sources of carbon dioxide in pond water.

Animal respiration / plant respiration / from air / bacterial respiration or decomposition

Photosynthesis

Explain how light intensity or carbon dioxide concentration may be varied.

Lamp / different distances (or wattages) OR sodium hydrogen carbonate / different

amounts

Photosynthesis

Each time light intensity or carbon dioxide concentration is varied a precaution is

necessary. What is this precaution and why is it necessary?

Precaution: Allow time (before counting bubbles)

Reason: Plant adjusting or equilibration or explained

Photosynthesis

Explain how you measured the rate of photosynthesis.

Counted bubbles (or measure volume) per unit time or use a (datalogging) sensor

Photosynthesis

Explain how you varied light intensity or carbon dioxide concentration.

Light source at different distances (from plant) or different wattages or different

concentrations of NaHCO3 solution

Photosynthesis—Light or CO2 Conc.

State how you kept another named factor constant.

Temperature / water bathOR light / source at different distances (from

plant) or different wattagesOR CO2 concentration / different concentrations of NaHCO3 solution

Photosynthesis

Suggest a suitable plant for such an investigation.

Aquatic plant or named, e.g. Elodea

Photosynthesis

How was the rate of photosynthesis measured?

Counted bubbles or measured volume / per unit time

OR Datalogging / named sensor (or mention of time)

Photosynthesis(i) Name a factor that must be kept constant

during this investigation. (ii) Explain how you would keep this factor

constant.(iii) Why is it necessary to keep it constant?

(i)Light (if CO2 addressed) or CO2 (if light addressed) or

temperature; (ii)Fixed lamp distance (or wattage) or NaHCO3 or

water bath; (iii)To ensure that any change is not due to that factor

Photosynthesis

How would you measure the rate of photosynthesis?

Number of bubbles or volume / in a fixed time

Photosynthesis

(i) Name an environmental factor that you would vary in this experiment.

(ii) Explain how you would vary the factor that you have named.

(i) Carbon dioxide or light or other factor

(ii) Addition of sodium hydrogen carbonate or changing distance of light source (must

correspond)

Photosynthesis—Light or CO2

Other environmental factors should be kept constant during the experiment. Name one of

these factors.

Light or carbon dioxide or temperature

Photosynthesis

Describe an activity that you carried out to investigate the influence of light intensity or carbon dioxide concentration on the rate of

photosynthesis.

Type of plant or named plant / control / factor kept constant / how variable altered / how rate

was measured / time / thermometer / water bath / adjust / bubbles / lamp / ruler / result

/conclusion / record / repeat / average

Photosynthesis

How did you vary the light intensity or the carbon

dioxide concentration?

Light: lamp at different distances from plant ORCO2 conc.: different concs. of NaHCO3 solution

Photosynthesis

How did you measure the rate of photosynthesis?

Counted number of bubbles / per unit time

Photosynthesis

What is the relationship between the rate of photosynthesis and either the light intensity or

the carbon dioxide concentration.

As either light intensity or CO2 conc. increases, the rate of photosynthesis increases

Photosynthesis

Name any two environmental factors affecting photosynthesis that you could have investigated

during the course of your practical work.

CO2 concentration / light intensity / temperature